- implemented DH protocol for PFS encryption in distant chat between GXS ids.
- changed format of keyId in rstlvkeys.{h,cc}, but kept the serialisation for backward compatibility (A #define needs to be removed to fix it for good). Updated rsrecogn, rsmsgitems, gxssecurity accordingly
- added "chat peer" in IdDialog to help testing distant chat.

Distant chat works and is now encrypted. The GUI still needs some smoothing: display of correct peer names
in chat window, remove the need to add a message in p3chatservice.cc:3217 to force poping up the chat window.

- added MsgAddress class to handle generic address types while keeping type separation in Messages. Not used yet.